Wagner was born on June 11, 1973, in Rennes, France. She took up the piano early and enrolled at the Conservatoire de Paris, studying with Dominique Merlet and earning a first prize. She continued at the Conservatoire, studying with Jean-François Heisser, but then she met pianist Leon Fleisher and, on his recommendation, moved to the Cadenabbia di Griante on Lake Como in Italy, where she had high-powered teachers, including Alexis Weissenberg, Murray Perahia, and Fleisher himself. She made her recording debut in 1996 on the Lyrinx label, issuing an album of music by Rachmaninov; she then recorded albums devoted to Scriabin, Mozart, and Schumann for that label and also issued an album of Brahms piano music on Naïve. In 1999, Wagner received the Instrumentalist Solo Revelation of the Year award at France's Victories de la musique classique ceremonies. In 2003, she began recording for the Ambroisie label, backing cellist Ophélie Gaillard on a recording of Benjamin Britten's Cello Sonata, Op. 65.
Wagner made several more recordings as a soloist for Ambroisie, beginning with Claude Debussy: Images Estampes in 2005. She then moved to Actes Sud, where she recorded several albums of contemporary music. Wagner performed for the first time at the Bouffes du Nord theater in Paris with electronic musician Murcof. The two continued to collaborate and issued several albums together on the InFiné label, beginning with Statea in 2016. Wagner ran as a candidate of the Animalist Party in France's 2017 legislative elections. In 2021, Wagner backed pianist Wilhem Latchoumia on the album This Is America. She and Murcof returned the following year on InFiné with Study of the Invisible. ~ James Manheim, Rovi